In general, among waveguide corners, the H-corner and E-corner in which a rectangular waveguide is bent, for example, are known (see Non-Patent Document 1, for example). At this time, since the H-corner is bent so as to be parallel to a magnetic field H, the H-plane wall constituting the long side of a rectangular waveguide is bent 90 degrees. On the other hand, since the E-corner is bent so as to be parallel to an electric field E, the E-plane wall constituting the short side of a rectangular waveguide is bent 90 degrees.
Non-Patent Document 1: “Maikuroha-kairo no kiso to sono oyo (Basics and Applications of Microwave Circuit)”, Yoshihiro Konishi, Sogo-denshi-shuppansha, Aug., 1990, p 181
Now, in the above-described H-corner according to a related technology, since the H-plane wall is bent, although the plane of polarization of an electric field E is perpendicular to each other between the input side and the output side of the H-corner, the rectangular waveguide can be bent only in the direction parallel to the H-plane wall (direction perpendicular to the E-plane wall). On the other hand, since the E-plane wall is bent in the E-corner, although the rectangular waveguide can be bent in the direction perpendicular to the E-plane wall, the plane of polarization of an electric field E becomes parallel to each other between the input side and the output side of the H-corner, the plane of polarization cannot be freely selected. As a result, according to the related technology, the freedom of layout of a waveguide microwave circuit in which a plurality of waveguides are combined is low and there is a problem in that the waveguide circuit becomes larger.